The invention relates to apparatus for delimbing felled trees, and more particularly to boom delimbers.
In the modern, highly-automated logging operations, a specialized machine is often used to delimb trees which have been felled and stacked by another machine. For example, according to one existing tree harvesting operation, a feller-buncher will fell trees and stack them in a central landing. A delimbing apparatus then is used to strip the logs of branches so that they may be more readily transported and processed.
A standard existing delimbing machine is mounted on a tracked vehicle. It has a long boom which may be horizontally extended, and a delimbing head at the end of the boom. The head is equipped with delimbing knives. The entire boom is pivoted on the vehicle. To operate the delimber, the boom is extended and the delimbing head grasps the tree, using grapple jaws. The boom is then retracted to place the end of the tree in holding arms which are fixed with respect to the vehicle. The boom is then again extended along the length of the tree, with the delimbing knives acting to cut off branches as the boom is extended. Once the entire length of the tree has been delimbed by the extended boom, the tree is returned to the stack. Typically the delimbing head will also have a topping knife or saw to cut off the top end of the tree, and may also have a device for measuring the length of the tree which has been delimbed.
A problem with existing delimber designs is that the pivot point for the boom is generally on the front edge of the supporting vehicle. Because the boom extends a very long distance from the vehicle, to avoid the vehicle tipping over a large counterweight is required, or it is necessary to utilize a larger supporting vehicle. In some cases it is also necessary to extend the length of the caterpillar tracks to provide a broader base. Also, problems have been encountered in the measuring function of the boom in that rollers are used which spin on the surface of the log.
The present invention overcomes these problems by providing a delimber apparatus in which the log is conveyed through the delimbing knives, rather than extending the delimbing knives along the length of the log. Traction arms are provided which grip the log and drive it lengthwise through the delimber head. This design also facilitates the accurate measurement of the length of the log. Also, in the present invention, the pivot point is located back from the front edge of the carrying vehicle, and a pivotable base is provided which allows the delimbing apparatus to be lowered to a compact position for transport.